Conventionally, hybrid vehicles are separately equipped with cooling circuits in various temperature ranges: e.g., a high-temperature range (approximately 100° C.) for engine cooling, an intermediate-temperature range (approximately 60° C.) for cooling an inverter and a motor generator, and a low-temperature range (40° C.) for cooling a battery pack.
In this way, various cooling circuits are mounted on the vehicle, which cause problems, such as a complicated configuration of the cooling circuits, or deterioration in mountability.
In hybrid vehicles, when the vehicle interior is intended to be heated using waste heat from an engine or a power-train device as a heat source, the heat is often insufficient, failing to adequately heat the interior.
As a countermeasure for this, vehicles with heat pump cycles mounted have also been developed. This technique uses the heat-pump cycle to absorb heat from the outside air, thereby heating the vehicle interior. Such a technique, however, dissipates waste heat from the engine or power-train device into the outside air without using the waste heat for heating, and thus has a problem that the heat cannot be efficiently used.
Note that Patent Document 1 discloses a thermal controller for a vehicle that can switch and circulate the coolants for two systems with respect to a motor generator and an inverter.